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Isosceles Triangles

A triangle in which two of the sides are equal is called an “Isosceles triangle”, and we often identify the equal side by tagging them with a short line:

Isosceles Triangle

The third side is called the "base", and we will prove that the angels at the two sides of the base (and opposite the two equal sides) are congruent.

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Now that we've explained the basic concept of isosceles triangles in geometry, let's scroll down to work on specific geometry problems relating to this topic.

isosceles triangle with bisector

Angle bisector is perpendicular to the base in an isosceles triangle

Base angles theorem in Geometry

Converse Base Angle Theorem

Angle bisector in triangle

Angle Bisector in a Triangle

Properties of Isosceles Triangles

Converse Angle Bisector Theorem for Isosceles Triangles

isosceles triangle with median

Isosceles Triangles: the Median to the Base is Perpendicular to the Base

Properties of Isosceles Triangles

Isosceles Triangles: the Height to the Base Bisects the Apex Angle

Properties of Isosceles Triangles

The Height to the Base of an Isosceles Triangle Bisects the Base

Base angles theorem in Geometry

Base Angles Theorem

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About

Welcome to Geometry Help! I'm Ido Sarig, a high-tech executive with a BSc degree in Computer Engineering and an MBA degree in Management of Technology. I'm here to tell you that geometry doesn't have to be so hard! My goal with this website is to help you develop a better way to approach and solve geometry problems, even if spatial awareness is not your strongest quality. Read More…

Geometry Topics

  • Area of Geometric Shapes
  • Circles
    • Arcs, Angles, and Sectors
    • Chords
    • Inscribed Shapes
    • Tangent Lines
  • Lines and Angles
    • Intersecting Lines and Angles
    • Parallel Lines
    • Perpendicular lines
  • Pentagons and Hexagons
  • Perimeter of Geometric Shapes
  • Polygons
  • Quadrangles
    • Kites (Deltoids)
    • Parallelograms
    • Rectangles
    • Rhombus
    • Squares
    • Trapezoids
  • Triangles
    • Congruent Triangles
    • Equilateral Triangles
    • Isosceles Triangles
    • Pythagorean Theorem
    • Right Triangles
    • Similar Triangles
    • Triangle Inequalities

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